Mast spreaders, are they under lots of pressure ?

[Dockhead]

Originally Posted by Andrew Troup

Excellent advice. One other point to keep the mast from inverting, which is often overlooked (it's a counsel of perfection, but worth thinking about when new sails are ordered)

Ideally the head of the sail in the deep reefed positions should fall at, or preferably a little above, the nearest attachment point of an inner forestay or babystay.

Are you sure that makes any difference? As far as I know, the load is not concentrated at the head of the sail -- it's spread across the luff. That's because unlike the case with a headsail, the main is not attached to a stay.

I am pretty sure it doesn't really make any difference; nevertheless, my deeply reefed position is with the top of the leech (it's not exactly the head, because I have in-mast furling) positioned opposite the point at which the inner forestay is attached to the mast. So the main is symmetrical with the staysail. I've always thought that this habit was just a bit of superstition on my part.

[Snowpetrel]

If you've got an inner forestay, and a reasonable section mast I don't think it's an issue.

[Andrew Troup]

Originally Posted by Dockhead

Are you sure that makes any difference? As far as I know, the load is not concentrated at the head of the sail -- it's spread across the luff. ....

Leech tensions are high on tall mainsails, and they appear at the masthead in the form of halyard tension pulling downwards, and a significant aftwards force from the horizontal component of the leech vector.

That aftwards force is responsible for the automatic depowering that you get in fractional rigs, as the increasing leech tension in puffs causes the topmast to curve aft.

And in masthead rigs, the nett longitudinal force at the masthead from the vector sum of the loads in the headsail luff, the forestay and backstay, and the leech load from the main, (the considerable leech load from the genoa or blade jib is virtually vertical so it doesn't really come into the picture) is as much as three quarters of the lateral load at the masthead.

It's directed aft.

If the backstay adjuster is released (or the stay fails !), as long as you're hard on the wind and the main remains sheeted hard with plenty of breeze, the forestay tension will not be lost, and in the case of an in-line rig, that's purely from the leech load on the mainsail.

[Weyalan]

If you use non-aluminium rivets (i.e. Monel, stainless, etc) into aluminium mast, make sure you use an appropriate anti-corrosion compound. I use Duralac, but there are others available too.